Which of these numbers is composite? ${3,\ 53,\ 63,\ 83,\ 89}$
Answer: A composite number is a number that has more than two factors (including 1 and itself). 3, 53, 83, and 89 each have only two factors. The factors of 63 are 1, 3, 7, 9, 21, and 63. Thus, 63 is the composite number.